Strictly a conventional war. No nukes.
Russians are more nationalistic and can be persuaded by societal structure to do what they’ve been doing for several hundred years: preserve their heritage.
USA: A bunch of educated enlistees who would KNOW that war is wrong AND the magnitude of it would scare them.
This one would be a draw. They have the same resources, strong enough allies, equal amount of people to draft. BUT, they’ve been through this MANY times and wouldn’t back down because they don’t have the input from the people they way we do. Like, Putin isn’t going to worry abut getting re-elected.